小编Ben*_*n H的帖子

body {
  background: lightblue;
  font-family: sans-serif;
}
div {
  background: purple;
  width: 200px;
  padding: 30px;
  border: 3px solid white;
  color: white;
}

<div>Some Text</div>

// The number of characters
    var yourElement = $('h1.latest');
    var charLength = yourElement.text().length;
    if(charLength < 20){
       yourElement.addClass('pt45');
    }

.pt45 {
    font-size: 10px;
    color:red;
}

<h1 class="latest">123456789</h1>
<h1 class="latest">123456789123456789123456789123456789</h1>